Farnesoid X receptor targeting to treat nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver condition evolving in a proportion of patients into nonalcoholic steatohepatitis (NASH), an aggressive form of NAFLD associated with increased cardiovascular mortality and significant risk of progressive liver disease, including fibrosis, cirrhosis and hepatocellular carcinoma. At present, no specific therapies for NASH exist. In this review, we examine the evidence supporting activation of the farnesoid X receptor (FXR), a nuclear hormone receptor regulated by bile acids (BAs), for the treatment of NASH. We also discuss the potential of the semi-synthetic BA derivative obeticholic acid (OCA), a first-in-class FXR agonist, as a safe and effective drug to address this significant unmet medical need.     

Acanthoic acid modulates lipogenesis in nonalcoholic fatty liver disease via FXR/LXRs-dependent manner

OBJECTIVE To reveal the effect and mechanism of acanthoic acid(AA) on nonalcoholic fatty liver disease(NAFLD) associated with lipid accumulation by activating Farnesoid X receptor(FXR) and liver X receptors(LXRs) signaling. METHODS C57 BL/6 mice were received a modified Lieber-De Carli diet with 71%high-fat(L-D) and treated with AA(20 and 40 mg·kg~(-1)) or equal volume of saline for 12 weeks. The regulation of AA on lipid accumulation was also detected in pro-steatotic stimulated AML12 cells with palmitic acid(PA).RESULTS When L-D diet-fed mice were treated with AA, loss in body mass, liver index, and liver lipid droplet were observed along with reduced triglyceride(TG) and serum transaminase. Furthermore, AA decreased sterol regulatory element binding protein 1(SREBP-1) and target genes expression, regulated PPARα and PPARγ expressions, ameliorated hepatic fibrosis markers, enhanced hepatic FXR and LXR, and regulated AMPK-LKB1 and SIRT1 signaling pathway. Moreover, AA attenuated lipid accumulation via FXR and LXR activation in steatotic AML-12 cells, which was confirmed by guggulsterones(FXR antagonist) or GW3965(LXR agonist). CONCLUSION Activation of FXR and LXR signaling caused by AA might increase AMPK-SIRT1 signaling and then contribute to modulating lipid accumulation and fatty acid synthesis, which suggested that activated FXR-LXR axis by AA represented an effective strategy for relieving NAFLD.     

利拉鲁肽治疗非酒精性脂肪性肝病的作用机制及研究进展

非酒精性脂肪性肝病（NAFLD）是我国最常见的慢性肝脏疾病之一。大多数病人的肝脂肪变性的发展与饮食中的脂肪摄入有关,其特征为自由脂肪酸摄入增加和肝脏脂肪重新生成,肝细胞中三酰甘油过度积聚。非酒精性脂肪性肝炎是一种由单纯性肝脂肪性变进展为肝细胞死亡、炎症浸润和纤维化状态的代谢性肝病,是NAFLD较严重的状态,是肝硬化、肝癌的重要危险因素。胰高血糖素样肽-1(GLP-1)是回肠内分泌细胞分泌的一种脑肠肽,进餐后血糖升高刺激胰高血糖素样肽-1分泌,抑制α细胞分泌胰高血糖素,防止餐后高血糖。以往的研究中,GLP-1受体激动剂被明确批准用于治疗糖尿病和肥胖症。其中,GLP-1受体激动剂利拉鲁肽除了其降血糖效果外,还对NAFLD存在有益的影响。该文对利拉鲁肽在NAFLD中的作用及机制研究进展做一综述。     

Farnesoid X receptor agonist for the treatment of liver and metabolic disorders: focus on 6-ethyl-CDCA

6-ethyl-chedeoxycholic acid (6E-CDCA) is a farnesoid X receptor (FXR) ligand endowed with agonistic activity under development for treatment of cholestatic liver diseases including primary biliary cirrhosis (PBC) and liver-related metabolic disorders including non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). FXR is a bile sensor that acts in coordination with other nuclear receptors to regulate essential steps of bile acid uptake, metabolism and excretion. 6E-CDCA has been investigated in preclinical models of cholestasis, liver fibrosis and diet-induced atherosclerosis. In a phase II clinical trial in patients with PBC, 6E-CDCA met the primary endpoint of a reduction in alkaline phosphatase levels but safety data indicated that the drug exacerbated pruritus, one of the main symptoms of PBC, suggesting that 6E-CDCA or FXR are mediators of pruritus in humans. Treatment of patients with diabetes and liver steatosis resulted in amelioration of insulin sensitivity despite a reduction a slight reduction in HDL and increased levels of LDL were observed. These side effects on bile acids and lipid metabolism were all predicted by pre-clinical studies, suggesting that potent FXR ligands hold promise but potential side effects might limit their development.     

Are statins ‘IDEAL’ for non-alcoholic fatty liver disease?

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and cause of elevated serum liver enzyme activities in the developed world1. Obesity, diabetes mellitus (DM), and dyslipidaemia, common components of the metabolic syndrome (MetS), are frequently associated with NAFLD; 75–100% of patients with MetS or DM have NAFLD2. NAFLD is characterized by hepatic triglyceride (TG) infiltration in the absence of alcohol abuse or chronic liver disease1. NAFLD includes a spectrum of conditions varying from steatosis to steatosis with inflammation [steatohepatitis (NASH)], necrosis, fibrosis or cirrhosis that rarely progresses to hepatocellular carcinoma3. NAFLD and NASH are the hepatic manifestations of MetS and are associated with increased cardiovascular disease (CVD) risk4. Most NAFLD/NASH patients die from CVD rather than from liver disease4,5. There is no universally accepted treatment for NAFLD1-5.     

Bile acid receptors in non-alcoholic fatty liver disease

Accumulating data have shown that bile acids are important cell signaling molecules, which may activate several signaling pathways to regulate biological processes. Bile acids are endogenous ligands for the farnesoid X receptor (FXR) and TGR5, a G-protein coupled receptor. Gain- and loss-of-function studies have demonstrated that both FXR and TGR5 play important roles in regulating lipid and carbohydrate metabolism and inflammatory responses. Importantly, activation of FXR or TGR5 lowers hepatic triglyceride levels and inhibits inflammation. Such properties of FXR or TGR5 have indicated that these two bile acid receptors are ideal targets for treatment of non-alcoholic fatty liver disease, one of the major health concerns worldwide. In this article, we will focus on recent advances on the role of both FXR and TGR5 in regulating hepatic triglyceride metabolism and inflammatory responses under normal and disease conditions.     

PPAR激动剂在治疗非酒精性脂肪性肝病中的应用前景

由于肥胖症和2型糖尿病患者越来越多,非酒精性脂肪性肝病(NAFLD)也呈现逐年上升趋势。NAFLD可引起肝硬化和肝癌等并发症,严重威胁公众健康,目前尚无有效治疗NAFLD及其并发症的药物。肝脏甘油三酯聚集是NAFLD的重要标志,过氧化物酶体增殖物活化受体(PPAR)可参与脂代谢、糖代谢以及炎症的调控。本文综述了PPAR参与NAFLD的可能作用机制以及治疗NAFLD的PPAR激动剂的研究进展。     

Obeticholic acid and budesonide for the treatment of primary biliary cirrhosis

Introduction: Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease of adults. Treatments are needed when patients have incomplete response to ursodeoxycholic acid (UDCA).

Areas covered: Discoveries of the key role played by bile acids (BAs) and nuclear receptors (NRs) in regulating liver and metabolic homeostasis have led to promising therapeutic approaches in liver diseases. A PubMed search for the recent literature on NRs in liver disease was conducted. In particular, obeticholic acid (OCA) is a farnesoid X receptor (FXR) agonist that has an important role in the enterohepatic circulation of BAs. Preliminary studies of OCA in patients with PBC have demonstrated marked biochemical improvement when administered in combination with UDCA and alone. Pruritus is the most common side effect, limiting treatment at higher doses. Budesonide is a glucocorticoid receptor/pregnane X receptor (PXR) agonist also involved in BA synthesis, metabolism and transport. Studies with budesonide have shown positive effects of short-term combination therapy in selected patients with early stage disease and overlapping features of autoimmune hepatitis.

Expert opinion: Though larger studies are needed, preliminary results of agents targeting FXR and PXR have been encouraging, particularly in subsets of patients with PBC and may mark a new therapeutic era.     

高脂饮食对非酒精性脂肪肝大鼠肝脏过氧化物酶体增殖物活化受体γ表达的影响

目的探讨过氧化物酶体增殖物活化受体(PPARγ)在高脂饮食所致非酒精性脂肪肝(NAFLD)大鼠肝脏的表达及其意义。方法模型组Wistar大鼠给予高脂饮食饲养,分批于实验第4、8、12周处死,设普通饮食饲养大鼠作对照。测定空腹血糖(FBG)、空腹胰岛素(FINS),计算胰岛素敏感指数(ISI);测定血清丙氨酸转氨酶(ALT)、天冬氨酸转氨酶(AST)、总胆固醇(TC)、甘油三酯(TG);苏木素-伊红(HE)染色观察肝组织病理变化;反转录聚合酶链反应(RT-PCR)分别检测大鼠肝脏PPARγmRNA的表达。结果模型组大鼠第4周呈现单纯性脂肪肝,第8~12周从单纯性脂肪肝进展为脂肪性肝炎,个别出现肝纤维化;RT-PCR显示,随着造模时间延长,肝脏PPARγmRNA的表达逐渐减弱,于第12周达到最低。结论持续12周的高脂饮食可以成功复制大鼠NAFLD模型;模型大鼠肝脏PPARγmRNA表达随造模时间的延长而逐渐减弱,PPARγ可以通过对胰岛素抵抗的调控参与NAFLD的发生发展。     

PPAR agonists reduce steatosis in oleic acid-overloaded HepaRG cells

Although non-alcoholic fatty liver disease (NAFLD) is currently the most common form of chronic liver disease there is no pharmacological agent approved for its treatment. Since peroxisome proliferator-activated receptors (PPARs) are closely associated with hepatic lipid metabolism, they seem to play important roles in NAFLD. However, the effects of PPAR agonists on steatosis that is a common pathology associated with NAFLD, remain largely controversial. In this study, the effects of various PPAR agonists, i.e. fenofibrate, bezafibrate, troglitazone, rosiglitazone, muraglitazar and tesaglitazar on oleic acid-induced steatotic HepaRG cells were investigated after a single 24-hour or 2-week repeat treatment. Lipid vesicles stained by Oil-Red O and triglycerides accumulation caused by oleic acid overload, were decreased, by up to 50%, while fatty acid oxidation was induced after 2-week co-treatment with PPAR agonists. The greatest effects on reduction of steatosis were obtained with the dual PPARα/γ agonist muraglitazar. Such improvement of steatosis was associated with up-regulation of genes related to fatty acid oxidation activity and down-regulation of many genes involved in lipogenesis. Moreover, modulation of expression of some nuclear receptor genes, such as FXR, LXRα and CAR, which are potent actors in the control of lipogenesis, was observed and might explain repression of de novo lipogenesis.     

缬沙坦胶囊治疗伴有非酒精性脂肪肝的高血压患者的疗效观察

目的探讨缬沙坦胶囊治疗伴有非酒精性脂肪肝（NAFLD）的高血压患者的疗效。方法将符合纳入标准患者随机分成试验组和对照组。试验组给予缬沙坦胶囊;对照组给予氨氯地平片。比较两组血压、肝脏超声、肝功能、血脂、胰岛素抵抗指数（RI）的差别及临床疗效。结果缬沙坦胶囊组总有效率（93.24%）显著高于对照组（81.08%）,差异有统计学意义（χ^2=4.891,P=0.027）;治疗后,试验组谷丙转氨酶、胆固醇、甘油三酯、低密度脂蛋白及RI均显著低于对照组,差异有统计学意义（P〈0.05）。结论缬沙坦胶囊治疗伴有NAFLD的高血压患者具有更好疗效。     

Ochratoxin A Induces Steatosis via PPARγ-CD36 Axis

Ochratoxin A(OTA) is considered to be one of the most important contaminants of food and feed worldwide. The liver is one of key target organs for OTA to exert its toxic effects. Due to current lifestyle and diet, nonalcoholic fatty liver disease (NAFLD) has been the most common liver disease. To examine the potential effect of OTA on hepatic lipid metabolism and NAFLD, C57BL/6 male mice received 1 mg/kg OTA by gavage daily. Compared with controls, OTA increased lipid deposition and TG accumulation in mouse livers. In vitro OTA treatment also promoted lipid droplets accumulation in primary hepatocytes and HepG2 cells. Mechanistically, OTA prevented PPARγ degradation by reducing the interaction between PPARγ and its E3 ligase SIAH2, which led to activation of PPARγ signaling pathway. Furthermore, downregulation or inhibition of CD36, a known of PPARγ, alleviated OTA-induced lipid droplets deposition and TG accumulation. Therefore, OTA induces hepatic steatosis via PPARγ-CD36 axis, suggesting that OTA has an impact on liver lipid metabolism and may contribute to the development of metabolic diseases.     

普罗布考干预大鼠非酒精性脂肪肝形成的作用及机制研究

目的：探究普罗布考对大鼠非酒精性脂肪肝形成作用的干预情况及干预机制。方法选取30只SD大鼠,将其随机分为空白组、高脂组及研究组,每组10只。给予相应喂养方法,通过高脂饮食诱发实验大鼠出现NAFLD,建立模型,喂养18周后,处死全部大鼠,并进行血脂及肝功能相关指数,即TC、TG、AST、ALT及HDL与LDL水平,计算肝脏指数同时检测其肝脏组织FXR、SHP及SREBP-1c mRNA表达情况。结果3组大鼠肝脏病变程度均以高脂组最高,空白组最低,研究组脂肪性病变、炎性程度及纤维化病变评分分别为（2?．97±0．18）分、（1．29±0．27）分及（0．05±0．02）分,均位于其他2组评分之间。高脂组与研究组TC、ALT、AST及LDL与空白组比较均明显升高,且高脂组升高程度更为明显（ P ＜0．05）,空白组FXR、SHP及SREBP-1c的mRNA水平分别为（0．92±0．42）β-actin、（1．01±0．60）β-actin、（0．68±0．27）β-actin,各检测项目均显著高于高脂组（ P ＜0．05）,研究组FXR、SHP的mRNA表达水平位于其他2组之间,分别为（0．28±0．13）β-actin及（0．42±0．23）β-actin,差异有统计学意义（ P ＜0．05）,而SREBP-1c的mRNA表达水平为（0．68±0．22）β-actin,与空白组基本相同（ P ＞0．05）。结论普罗布考对由高脂饮食导致的大鼠NAFLD症状具有一定的预防作用,可明显减轻由该因素导致的大鼠肝脏出现脂肪性样变情况,其预防机制为该药物提高了大鼠机体的抗氧化能力,从而降低了组织出现氧化应激而导致的损伤。     

Berberine reducing insulin resistance by up-regulating IRS-2 mRNA expression in nonalcoholic fatty liver disease (NAFLD) rat liver

This study was performed to investigate the molecular mechanism and the therapeutic effect of berberine on nonalcoholic fatty liver disease (NAFLD). Rat models were given a high-fat diet (42% kcal) until they developed NAFLD, then were given normal saline (n = 10), berberine (n− = 10) at 187.5 mg/kg/day, or pioglitazone (n = 10) at 10.0 mg/kg/day intragastrically for 4 weeks, respectively, and evaluated by hyperinsulinemic euglycemic clamping for insulin sensitivity. Serum biochemical markers and liver triglyceride (TG) were analyzed, real-time RT-PCR for mRNA expression and western blotting for protein expression of insulin receptor (IR) and insulin receptor substrate-2 (IRS-2) in liver tissues were performed, and hepatic histopathology in the rat models with NAFLD at the end of treatment was compared with normal controls (n = 10). The NAFLD rats developed insulin resistance, showing increased fasting blood glucose and insulin levels, decreased glucose infusion rate, increased weight of epididymal fat (g/100 g body weight), obvious hepatic steatosis and inflammation, and down-regulated IRS-2 mRNA and protein levels compared with normal controls (all P < 0.05). In comparison with those treated with saline, model rats treated with berberine or pioglitazone underwent significant recovery, including up-regulated IRS-2 mRNA and protein (all P < 0.05). Our results indicate that berberine may improve insulin resistance of NAFLD by up-regulating mRNA and protein levels of IRS-2, a key molecule in the insulin signaling pathway, suggesting that berberine may be used to treat NAFLD.     

FXR as a novel therapeutic target for vascular disease

Diseases such as atherosclerosis involve large blood vessel narrowing and hardening, an increase in activated and inflammatory cells, and an accumulation of lipids such as cholesterol. The farnesoid X receptor (FXR) is a recently identified steroid-like receptor. Bile acids are FXR ligands, which use FXR feedback to limit their own biosynthesis in the liver from cholesterol. FXR ligands have been proposed as novel targets in cardiovascular disease, as they affect lipid metabolism in the liver and gastrointestinal tract and lower circulating triglycerides and cholesterol. Recent evidence also suggests that FXR is expressed in the vasculature, implicating FXR as a novel potential 'direct' target for cardiovascular diseases. This review aims to introduce the FXR literature and discuss the mechanisms by which FXR may both directly and indirectly affect the progression of cardiovascular disease.     

非酒精性脂肪性肝病发病机制的研究进展

非酒精性脂肪性肝病（NAFLD）是指与过量饮酒无关的临床综合征,主要病理改变包括肝细胞弥漫性脂肪变性和脂肪堆积。NAFLD动物模型表现出显著的肝脏微循环障碍,关于其形成机制,被广为接受的为＂二次打击＂学说。该学说认为肥胖、胰岛素抵抗等因素作为＂第一次打击＂,导致肝脏中脂质堆积,形成单纯性脂肪肝,增加了＂第二次打击＂造成的肝脏损伤的易感性,这些因素包括炎症、枯否细胞功能障碍、氧化应激、线粒体障碍、脂肪因子调节紊乱等,导致非酒精性脂肪性肝炎甚至纤维化等更严重疾病的发生。